WO2014192705A1 - Sheet for agricultural use - Google Patents

Abstract

Provided is a sheet for agricultural use, which has a high reflectance, excellent water shielding properties, excellent water vapor permeability and excellent air permeability, and is capable of maintaining water resistance. A sheet for agricultural use (10) according to the present invention is provided with a sheet base (11) and a light-reflecting layer (12) that is provided on one surface of the sheet base (11). The sheet base (11) is composed of a porous thermoplastic resin sheet that has voids (13) having an average diameter within the range of from 1 μm to 50 μm (inclusive), a void fraction within the range of from 35% to 60% (inclusive) and a thickness within the range of from 30 μm to 90 μm (inclusive). The light-reflecting layer (12) has a thickness within the range of from 0.5 μm to 4 μm (inclusive).

Description

Agricultural sheet

The present invention relates to an agricultural sheet, and more particularly to an agricultural sheet that can be suitably used for multi-cultivation of crops such as citrus fruits such as mandarin oranges, deciduous fruit trees such as peaches and strawberries, and vegetables.

Multi-cultivating technology is attracting attention in order to improve the quality and differentiation of crops such as fruits, vegetables and flowers. Multi-cultivation is a cultivation method for controlling the state of cultivated soil (ground) in order to obtain good quality crops without being affected by the weather during cultivation. In conventional multi-cultivation, vinyl sheets have been used as agricultural sheets, but since the sheets do not have air permeability, applying vinyl sheets immediately after rainfall or irrigation makes it impossible to drain soil, In some cases, root rot occurred. In recent multi-cultivation and the like, multi-seats suitable for various multi-cultivation have been developed, and the soil state is controlled by laying multi-seats on soil in which trees are planted. By laying such a multi-sheet on the soil, the penetration of rainwater into the soil is suppressed, the moisture in the soil is evaporated, the amount of water in the soil is kept appropriate, and carbon dioxide in the soil is removed from the outside air. Can be released inside.

¡Multi-sheets are required to have excellent water barrier properties, moisture permeability and breathability. As such a sheet, for example, a non-work cloth sheet formed using a non-work cloth is used (for example, Japanese Patent Application Laid-Open No. 2003-333940). In Japanese Patent Laid-Open No. 2003-333940, as a multi-sheet, a light-reflective resin layer is formed on at least a part of the surface of the unwoven cloth sheet made of long-fiber unwoven cloth so that the light reflectivity is not less than a predetermined value. A reflective multi-sheet has been proposed. According to the cited document 1, by using such a light-reflective multi-sheet as an agricultural sheet, light transmission to the soil is suppressed, and there is a herbicidal effect, and an increase in summer temperature can be suppressed. ing.

¡The unemployed cloth sheet has a lower strength than the vinyl sheet, so that the service life is shortened when working on the unemployed cloth sheet or when the agricultural machine runs. Further, due to the structure of the nonwoven fabric, it is difficult to accurately control the water shielding and moisture permeability. Therefore, it has also been proposed to use a resin sheet having moisture permeability as a multi-sheet. For example, in JP-A-3-280816 and JP-A-4-166622, moisture permeability is obtained by forming a film from a raw material in which a thermoplastic resin such as an olefin resin is blended with a filler such as calcium carbonate. It has been proposed that a porous film with a large thickness can be obtained and used as a sheet for multi-cultivation.

JP 2003-333940 A JP-A-3-280816 Japanese Patent Laid-Open No. 4-166022

The porous plastic film as described above has water barrier properties, moisture permeability, and air permeability and excellent durability when cultivating crops, but has insufficient light reflectivity. Met. By the way, citrus fruits such as mandarin oranges and deciduous fruit trees such as peaches and persimmons reflect the sunlight incident on the soil surface to give the trees sufficient light, and the growth of the trees is promoted. It is known that sugar content is improved. Therefore, it is considered that the production efficiency of crops such as citrus fruits and deciduous fruit trees will be further improved by using a porous plastic film with excellent light reflectivity on the film surface as a multi-sheet covering the soil. .

The present inventors have examined such a multi-sheet, and although the reflectance of the film is improved by providing a light reflecting layer on one surface side of the porous thermoplastic resin sheet, moisture permeability and air permeability are improved. I noticed it would drop. And on one surface side of the porous thermoplastic resin sheet having a specific thickness, by applying a white ink or the like so as to have a specific thickness and providing a light reflection layer, water impermeability, moisture permeability, air permeability and It was found that a film having excellent light reflectivity can be realized while maintaining durability. The present invention is based on this finding.

Therefore, an object of the present invention is to provide an agricultural sheet having high reflectivity, excellent water shielding properties, moisture permeability and air permeability, and capable of maintaining water resistance.

An agricultural sheet according to the present invention is an agricultural sheet comprising a sheet base material and a light reflection layer provided on at least one surface side of the sheet base material,
The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
The thickness of the light reflection layer is in the range of 0.5 μm or more and 4 μm or less.

In the present invention, the thickness of the light reflecting layer is preferably in the range of 0.5 μm or more and 4 μm or less.

In the present invention, it is preferable that the porous thermoplastic resin sheet comprises a polypropylene resin.

In the present invention, it is preferable that the porous thermoplastic resin sheet is stretched at least in a uniaxial direction.

In the present invention, the sheet base material is preferably a laminate of two or more layers of the stretched porous thermoplastic resin sheet.

In the present invention, it is preferable that the sheet base material is formed by laminating two or more layers so that the stretching axis directions of the respective porous thermoplastic resin sheets are orthogonal to each other.

In the present invention, the light reflection layer preferably contains a white pigment and a polyurethane resin.

In addition, the method for cultivating crops according to another aspect of the present invention includes:
A method for cultivating crops using an agricultural sheet,
The agricultural sheet includes a sheet base material, and a light reflection layer provided on at least one surface side of the sheet base material,
The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
The thickness of the light reflecting layer is in the range of 0.5 μm or more and 4 μm or less,
The agricultural sheet is laid on the soil surface on which the crop is planted so that the surface on the sheet base material side faces the soil side.

Furthermore, the method of using the agricultural sheet according to another aspect of the present invention includes:
The agricultural sheet includes a sheet base material, and a light reflection layer provided on at least one surface side of the sheet base material,
The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
The thickness of the light reflecting layer is in the range of 0.5 μm or more and 4 μm or less,
The agricultural sheet is laid on the soil surface so that the surface on the sheet substrate side faces the soil side.

According to the present invention, by providing a light reflecting layer on the surface of the sheet base material, the reflectance of light incident on the agricultural sheet can be improved. It has moisture permeability and breathability and can maintain water resistance.

It is sectional drawing which shows simply the structure of the agricultural sheet | seat which concerns on embodiment of this invention. It is sectional drawing which shows simply the other structure of the agricultural sheet | seat which concerns on embodiment of this invention. It is a perspective view which shows an example which extends | stretches a thermoplastic resin sheet and forms a sheet | seat base material. It is a perspective view which shows an example which extends | stretches the laminated body of a thermoplastic resin sheet, and forms a sheet | seat base material. It is explanatory drawing which shows the state of movement of agricultural water | moisture content and a carbon dioxide gas. It is explanatory drawing which shows the reflective state of the rain in an agricultural sheet | seat. It is explanatory drawing which shows the reflective state in the agricultural sheet | seat of sunlight. It is a top view which shows an example of the cultivation soil in the case of applying an agricultural sheet | seat to cultivation soil. It is a top view which shows another example of the cultivation soil in the case of applying an agricultural sheet | seat to cultivation soil.

Hereinafter, modes for carrying out the present invention (hereinafter referred to as embodiments) will be described in detail with reference to the drawings. In addition, this invention is not limited by the following embodiment. In addition, constituent elements in the following embodiments include those that can be easily assumed by those skilled in the art and those that are substantially the same. Furthermore, the constituent elements disclosed in the following embodiments can be appropriately combined. Further, for convenience of explanation of the layer structure and the like, in the example shown below, the sheet base material installed on the ground will be described together with a diagram arranged below, but the present invention is not necessarily used in this arrangement. Do not mean. In the following description, one of the layers in the thickness direction may be referred to as “up” or “up”, and the other of the layers in the thickness direction may be referred to as “down” or “down”.

<Agricultural sheet>
An embodiment of an agricultural sheet according to the present embodiment will be described. 1 and 2 are cross-sectional views simply showing the configuration of an agricultural sheet according to an embodiment of the present invention. As shown in FIG. 1, the agricultural sheet 10 includes a sheet base material 11 and a light reflection layer 12. The agricultural sheet 10 is configured by laminating a sheet base material 11 and a light reflection layer 12 in the order of the sheet base material 11 and the light reflection layer 12. Moreover, in embodiment of this invention, as shown in FIG. 2, the sheet | seat base material 10 which comprises the agricultural sheet | seat 10 has several layers (In FIG. 2, the surface base material sheet | seat base material 11b, for base material layers. It may be composed of a sheet base material 11a and a surface layer sheet base material 11b).

[Sheet substrate]
The sheet base 11 is made of a porous thermoplastic resin sheet. The porous thermoplastic resin sheet contains a thermoplastic resin and a filler.

(Thermoplastic resin)
Thermoplastic resins include homopolymers of olefins such as ethylene, propylene, butene, hexene or copolymers of two or more olefins, one or more olefins and one or more polymerizable monomers that can be polymerized with the olefins. Resins such as copolymers, acrylic resins such as polymethyl acrylate, polymethyl methacrylate, and ethylene-ethyl acrylate copolymers, butadiene-styrene copolymers, acrylonitrile-styrene copolymers, polystyrene, styrene-butadiene -Styrene resins such as styrene copolymers, styrene-isoprene-styrene copolymers, styrene-acrylic acid copolymers, vinyl fluoride resins such as vinyl chloride resins, polyvinyl fluoride, polyvinylidene fluoride, 6- Nylon, 6,6-nylon, 1 -Amide resins such as nylon, saturated ester resins such as polyethylene terephthalate and polyprebutylene terephthalate, polycarbonate, polyphenylene oxide, polyacetal, polyphenylene sulfide, silicone resin, thermoplastic urethane resin, polyetheretherketone, polyetherimide, various types Examples thereof include thermoplastic elastomers and crosslinked resins. These may be one type or a combination of two or more types of thermoplastic resins. Among the above, polyolefin resins can be preferably used from the viewpoints of heat resistance, water resistance, chemical resistance, cost and the like.

Examples of the monomer unit constituting the polyolefin resin include ethylene, propylene, butene, hexene and the like. Specific examples of the polyolefin resin include polyethylene resins such as low density polyethylene, linear polyethylene and high density polyethylene, polypropylene resins such as propylene homopolymer and propylene-ethylene copolymer, poly (4-methylpentene- 1), poly (butene-1), ethylene-vinyl acetate copolymer and the like. Among these, a polypropylene resin is preferable. In addition to the polypropylene resin, the polypropylene resin is mainly composed of propylene as a monomer unit, ethylene, 1-butene, 1-pentene, 4-methyl-1-pentene, 1-hexene, 1-heptene, 1- Resins copolymerized with α-olefins such as octene, 1-nonene, 1-decene, etc. can be preferably used. The copolymer may be a binary, ternary, or quaternary system, and may be a random copolymer or a block copolymer.

When the polyolefin resin as described above is used as the thermoplastic resin, it is preferable that an olefin wax is blended. The olefin wax acts as a plasticizer, and when the porous thermoplastic resin sheet is stretched to form the sheet base material 11, it becomes easy to stretch. Examples of olefin waxes include ethylene homopolymers, ethylene resin waxes such as ethylene-α-olefin copolymers, propylene homopolymers, propylene resin waxes such as propylene-ethylene copolymers, poly (4- And methyl-pentene-1), poly (butene-1), and ethylene-vinyl acetate copolymer wax. Among the above, an ethylene-α-olefin copolymer can be preferably used.

(filler)
As will be described later, the filler is used to generate fine voids 13 in the sheet base material 11 when the thermoplastic resin sheet is stretched to form the sheet base material 11. As the filler, a known inorganic filler or organic filler can be used, and it is not particularly limited. Examples of the inorganic filler include heavy calcium carbonate, light calcium carbonate, calcined clay, talc, silicon oxide, diatomaceous earth, titanium oxide, magnesium oxide, zinc oxide, and barium sulfate. These may be surface-treated with a fatty acid or the like. Among these, heavy calcium carbonate, light calcium carbonate, calcined clay, and talc are preferable because they are inexpensive and have good moldability. As the inorganic filler, those having an average particle size of usually 0.01 μm or more and 15 μm or less, preferably 0.01 μm or more and 8 μm or less can be suitably used. The “average particle size” is defined as a statistical average value of particle size distribution measured on a volume basis, and is a known particle size distribution measuring device (for example, trade name “LA-920”, manufactured by Horiba, Ltd.). ) Means the value measured by.

The organic filler is preferably a resin different from the polypropylene resin and incompatible with the polypropylene resin. As the organic filler, a resin having a melting point of 120 ° C. or higher and 300 ° C. or lower, or a glass transition temperature Tg of 120 ° C. or higher and 280 ° C. or lower is used. Examples of organic fillers include polyethylene terephthalate, polybutylene terephthalate, polycarbonate, polyamide, polyethylene naphthalate, polystyrene, melamine, polyethylene sulfite, polyimide, polyethyl ether ketone, polyether ether ketone, polyphenylene sulfite, and poly-4. -Methyl-1-pentene, polymethyl methacrylate, a cyclic olefin homopolymer, a copolymer of cyclic olefin and ethylene, and the like.

As the filler, one kind may be selected from inorganic fillers or organic fillers, and these may be used alone, or two or more kinds may be used in combination.

The content of the filler is preferably 1% by mass or more and 65% by mass or less, and more preferably 2% by mass or more and 55% by mass or less. If the content of the filler exceeds 65% by mass, the thermoplastic resin sheet is stretched easily when it is biaxially stretched in the step of stretching the thermoplastic resin sheet when forming the sheet substrate 11.

(Method for producing porous thermoplastic resin sheet)
The porous thermoplastic resin sheet is produced by forming a film composition of a resin composition for forming a sheet base material containing a thermoplastic resin and a filler with a known extruder and the like, and then performing a stretching process. Thermoplastic composed of two or more layers using a co-extrusion machine using different thermoplastic resins or using two or more resin compositions for forming a sheet base material with different filler mixing ratios A resin sheet may be formed.

The obtained thermoplastic resin sheet is stretched by a known method. By stretching a thermoplastic resin sheet comprising a resin composition for forming a sheet base material containing a filler, peeling occurs at the interface between the filler and the thermoplastic resin, and the peeling that occurs at this interface is the thermoplastic resin sheet. It is propagated and expanded by stretching. Thereby, the space | gap 13 is formed in a thermoplastic resin sheet, and a porous thermoplastic resin sheet can be obtained. As a method of stretching the thermoplastic resin sheet, a known stretching method can be used. For example, the thermoplastic resin sheet is stretched in a uniaxial or biaxial direction by longitudinal uniaxial stretching, longitudinal uniaxial multistage stretching, transverse uniaxial stretching, longitudinal and transverse sequential biaxial stretching, longitudinal and transverse simultaneous biaxial stretching, or a combination thereof. . In the present embodiment, the porous thermoplastic resin sheet is obtained by stretching the thermoplastic resin sheet in at least a uniaxial direction. Although the temperature at the time of extending | stretching is based also on the thermoplastic resin to be used, it extends | stretches in the temperature below the melting point below the glass transition temperature of a thermoplastic resin.

For example, as shown in FIG. 3, the sheet substrate 11 is formed by stretching a thermoplastic resin sheet 21 in at least a uniaxial direction in the MD (Machine Direction) direction or TD (Transverse Direction) direction. A sheet substrate 11 made of a plastic resin sheet is obtained. In addition, MD direction is an extrusion direction when extruding the resin composition for forming a sheet base material using an extruder, and TD direction is an extruding resin composition for forming a sheet base material using an extruder. This is a direction orthogonal to the extrusion direction at the time.

Moreover, the sheet base material 11 in which two or more layers of porous thermoplastic resin sheets are laminated can be produced by a co-extruder by using a resin composition for forming a sheet base material having different kinds or filler mixing ratios. . For example, as shown in FIG. 4, when manufacturing the sheet | seat base material 11 which laminated | stacked the porous thermoplastic resin sheet of 3 layers, the thermoplasticity of the outer layer side is carried out on both upper and lower sides of the thermoplastic resin sheet 21a of the inner layer side. Porous thermoplastic resin having different porosity on both surfaces of porous thermoplastic resin sheet 11a on the inner layer side by stretching laminate 22 in which resin sheet 21b is laminated at least in the uniaxial direction of MD direction or TD direction. The sheet base material 11 on which the sheet 11b is formed can be obtained.

When producing a base sheet composed of two or more porous thermoplastic resin sheets as described above, the porous thermoplastic resin sheets of each layer are preferably laminated so that the stretching axis directions do not coincide with each other. For example, when laminating other porous thermoplastic resin sheets 21b on both surfaces of a porous thermoplastic resin sheet 21a (for example, MD direction in FIG. 4) obtained by stretching in the longitudinal direction, Lamination is preferably performed such that the stretching axis direction (longitudinal direction) of the plastic resin sheet 21a and the stretching axis direction (for example, the TD direction in FIG. 4) of the porous thermoplastic resin sheet 21b to be laminated are orthogonal to each other. Thereby, the intensity | strength of the sheet | seat base material 11 can be made high.

As a multilayering method, the sheet base material forming resin composition for the base layer is fed to the surface layer sheet base forming resin composition immediately before flowing into the die manifold to obtain a laminate by multilayering. A laminated body is manufactured by a block method, a multi-manifold method using a multilayer manifold die, or the like.

In addition, a resin composition for forming a sheet base material containing a filler is formed using an extruder, and after removing the filler from the thermoplastic resin sheet, the thermoplastic resin sheet is stretched to form the voids 13. Also good. When removing the filler from the thermoplastic resin sheet, a liquid or the like is used. The liquid to be used is appropriately selected according to the type of filler in the thermoplastic resin sheet, but when the filler is essentially soluble in acid such as calcium carbonate, an acidic aqueous solution should be used. Can do. Examples of the method for removing the filler include a method in which a liquid is showered on a thermoplastic resin sheet, and a method in which the thermoplastic resin sheet is immersed in a tank containing the liquid. The method of removing the filler with the liquid may be batch or continuous, but is preferably continuous from the viewpoint of productivity. For example, the roll that rotates by putting the liquid in a tank in which two or more rolls are placed. The method of conveying a thermoplastic resin sheet | seat and making it pass in the liquid is mentioned. When the liquid is an acidic or alkaline aqueous solution, it is preferable to further wash the thermoplastic resin sheet from which the filler has been removed with water. When the thermoplastic resin sheet is washed, the thermoplastic resin sheet is usually washed to such an extent that a dissolved salt or the like does not precipitate in the thermoplastic resin sheet.

The thickness of the sheet substrate 11 is 30 μm or more and 90 μm or less, and preferably 40 μm or more and 80 μm or less. If the thickness of the sheet | seat base material 11 is in said range, since the sheet | seat 10 for agriculture is flexible and the intensity | strength is also hold | maintained, it is preferable. If the thickness of the sheet base material 11 is less than 30 μm, the rigidity as an agricultural sheet is not sufficient and the strength is insufficient. Moreover, the polyethylene multi-sheet conventionally used has a thickness of usually 15 μm or more and 20 μm or less, and it is preferable that the weight of the sheet base material 11 is light from the viewpoint of working efficiency of agricultural workers. If the thickness of the sheet base material 11 exceeds 90 μm, the weight as an agricultural sheet is unfavorable because handling is bad and the burden of work when an agricultural worker lays on the ground increases. In addition, when the thickness of the sheet base material 11 exceeds 90 μm, the amount of resin used in the sheet base material 11 increases, and thus the manufacturing cost of the agricultural sheet 10 increases. Therefore, when the thickness of the sheet base material 11 is within the above range, the sheet base material 11 is suitable as an agricultural sheet from the viewpoints of flexibility, strength, weight, manufacturing cost, workability of agricultural workers, and the like. Can be used.

The sheet base material 11 has the gap 13 as described above. As described above, the gap 13 is formed when the sheet base material-forming resin composition, the laminate, or the porous thermoplastic resin sheet is stretched to form the sheet base material 11. Alternatively, when the porous thermoplastic resin sheet is stretched, peeling occurs at the interface between the filler and the thermoplastic resin. The separation generated at the interface propagates by stretching the thermoplastic resin sheet 21 and expands, whereby the gap 13 is formed in the sheet base material 11.

As shown in FIG. 1, water vapor and carbon dioxide gas 15 from the ground pass through the gap 13 inside the sheet base material 11 and escape from the surface of the reflective layer 12 to the outside. In particular, when there is a gap 13 on the surface, the reflective layer 12 is formed thin and water vapor and carbon dioxide gas 15 are easily released.

The size of the gap 13 is preferably in the range of 1 μm or more and 50 μm or less in average diameter, more preferably in the range of 2 μm or more and 40 μm or less, and still more preferably in the range of 5 μm or more and 30 μm or less. is there. The size of the gap 13 is the diameter of the gap 13 in an arbitrary cross section in the stacking direction or stacking surface of the sheet base material 11. The thickness of the light reflection layer 12 tends to be thinner on the gap 13 than on the sheet substrate 11 without the gap 13. When the average diameter of the sheet base material 11 is less than 1 μm, the size of the gap 13 generated on the surface of the sheet base material 11 is small, so that the thickness of the light reflecting layer 12 laminated on the gap 13 is the gap 13. It is harder to become thinner than the light reflecting layer 12 on the sheet base material 11 having no surface. For this reason, the light reflecting layer 12 is not preferable because it is difficult to exhibit desired moisture permeability. When the average diameter of the sheet base material 11 exceeds 50 μm, the strength of the sheet base material 11 is remarkably lowered, which is not preferable. The shape of the gap 13 is various, such as a circle and an ellipse. The average diameter (L) of each gap and the maximum diameter (M) in the direction perpendicular thereto are measured and averaged [(L + M ) / 2] is the average diameter of each void. At least n (n is an integer of 1 or more) voids 13 are selected and measured repeatedly, and the average value is taken as the average diameter. The method for measuring the diameter of the gap 13 is to cut an arbitrary part from the sample, embed it with an epoxy resin, cut it with a microtome, etc., attach it to the sample stage, and deposit gold or gold-palladium etc. on the observation surface Then, the surface void shape is observed at an arbitrary magnification at which the cross section of the sample can be easily observed using, for example, a scanning electron microscope S-2400 manufactured by Hitachi, Ltd. In the present embodiment, the size of the gap 13 is determined by appropriately adjusting the addition amount of the filler, the draw ratio at the time of drawing the obtained thermoplastic resin sheet, the drawing temperature, and the like. It can be.

(Porosity)
The porosity of the sheet base material 11 is 35% or more and 60% or less, and more preferably 40% or more and 58% or less. Here, the porosity indicates the ratio of voids in the sheet base material 11 and can be calculated by the following formula I. In formula I, ρo represents the true density of the laminate, and ρ represents the density of the laminate. ρ is the density of the laminate in accordance with JIS P 8118. Unless the material before stretching contains a large amount of air, the true density is approximately equal to the density before stretching. The true density can be obtained by measuring and calculating by a dry density measuring method by a constant volume expansion method. For example, the true density can be measured using, for example, a dry automatic density meter “Acpic 1330” manufactured by Shimadzu Corporation, a multi-volume density meter “Acpic 1330 type” manufactured by Micromeritex Corporation, and the like.
Porosity (%) = {(ρ _o −ρ) / ρ _o } × 100 (I)

If the porosity of the sheet base material 11 is less than 35%, the water permeability and moisture permeability through which the water vapor and gas permeate the sheet base material 11 are deteriorated. Moreover, since the intensity | strength of the agricultural sheet | seat 10 will run short if the porosity of the sheet | seat base material 11 exceeds 60%, it is unpreferable. If the porosity of the sheet base material 11 is within the above range, the strength of the agricultural sheet 10 can be maintained while having air permeability.

The moisture permeability of the obtained sheet substrate 11 is usually 1,000 g / m ² · 24 hours or more, preferably 1,500 g / m ² · 24 hours or more. The water pressure resistance is 10 kPa or more, preferably 20 kPa or more. The sheet substrate 11 has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. If it exists in this range, a water vapor transmission rate and a water pressure resistance can be made into the said range.

The opacity of the sheet substrate 11 is preferably 70% or more and 100% or less. The opacity of the sheet substrate 11 conforms to JIS Z 8722. When the opacity of the sheet substrate 11 is less than 70%, it is difficult to visually recognize the appearance of the sheet substrate 11, which is not preferable.

The density of the sheet substrate 11 is preferably 0.50 g / cm ³ or more and 0.90 g / cm ³ or less. When the density of the sheet base material 11 is less than 0.50 g / cm ³ , the sheet strength is weak when the gap 13 is large and the average diameter is large. When the density of the sheet base material 11 is 0.90 g / cm ³ or more, there is no gap 13 or the average diameter is small. The preferable density of the sheet base material 11 is 0.50 g / cm ³ or more and 0.70 g / cm ³ or less.

(Additive)
Various additives such as a surfactant, a lubricant, and an antistatic agent can be arbitrarily added to the sheet base 11 as necessary.

Surfactant is used to prevent condensation of the sheet base material 11. As the surfactant, one or more of a group consisting of a nonionic surfactant, an anionic surfactant and an amphoteric surfactant can be used. Examples of the nonionic surfactant include glycerin fatty acid ester, pentaerythritol fatty acid ester, polyoxyethylene polyoxypropylene block polymer, and the like. Examples of the anionic surfactant include sulfonates and alkylbenzene sulfonates, and examples of the salts include sodium salts, potassium salts, and ammonium salts.

Examples of the lubricant include aliphatic hydrocarbons such as liquid paraffin, synthetic paraffin, and microcrystalline wax, stearic acid esters of linear alcohols, higher fatty acid amides, and the like.

The antistatic agent is kneaded and mixed with the resin composition for forming the sheet base material for forming the sheet base material 11 or applied to the surface of the sheet base material from which the antistatic agent is obtained. Antistatic performance can be imparted. Examples of the antistatic agent include cationic antistatic agents such as amines, imidazolines, amine oxide ethylene adducts, and quaternary ammonium salts; anionic antistatic agents such as phosphates, alkylallylphosphonic acids, adipic acid, and glutamic acid; Nonionic antistatic agents such as monohydric alcohols, polyhydric alcohol esters, higher alcohol ethylene oxide adducts, polyethers, alkylphenol ethylene oxide adducts, glycerin esters of fatty acids, fatty acid amides and their ethylene oxide adducts, and cationic groups Examples include amphoteric antistatic agents such as guanidine salts having both anionic groups and maleic anhydride acting on alkylamine, and sulfonic acids derived from polyethyleneimine. Preferred are alkyl diethanolamine, hydroxyalkyl monoethanolamine, glycerin fatty acid ester, polyglycerin fatty acid ester, alkylsulfonic acid soda, alkylbenzenesulfonic acid soda, tetraalkylammonium perchlorate, and the like. Any one of these may be appropriately selected depending on the glass transition temperature (glass transition point) Tg of the thermoplastic resin and processing conditions such as extrusion stretching, and these may be used alone or in combination of two or more. You may use it in combination. Further, the kneading and mixing of the resin composition for forming the sheet base material with the antistatic agent and the application of the antistatic agent to the surface of the sheet base material may be performed in combination.

[Light reflection layer]
The light reflecting layer 12 is a layer provided on at least one surface side of the sheet base material 11. The light reflection layer 12 is a layer that scatters light in the visible region and maintains moisture permeability that promotes evaporation of soil moisture. The sheet base material 11 has a high whiteness and has a performance of scattering light when the thickness is 90 μm or more. However, when the thickness of the light reflecting layer 12 is 90 μm or more, as described above, the sheet base material 11 becomes heavy, and when an agricultural worker winds the agricultural sheet 10 or spreads the agricultural sheet 10 on the ground. Since the work load tends to increase, the thickness of the sheet base material 11 is set to 30 μm or more and 90 μm or less. Therefore, since the reflectance is in the range of 50% or more and 90% or less with the sheet base material 11 alone, it is reflected by the sheet base material 11 on agricultural products such as citrus fruits and deciduous fruit trees that grow on trees planted on the ground. Cannot give enough light. On the other hand, since the agricultural sheet 10 according to the present invention is provided with the light reflecting layer 12 on the surface of the sheet base material 11, the reflectance of light in the visible region can be improved to, for example, 100%. .

The thickness of the light reflecting layer 12 is not less than 0.5 μm and not more than 4 μm. When the thickness of the light reflecting layer 12 is less than 0.5 μm, the light reflectance may be insufficient. On the other hand, as the thickness of the light reflection layer 12 is increased, the light reflectivity of the agricultural sheet 10 is improved, but the moisture permeability and breathability are impaired. In the present invention, the number and size of the gaps 13 formed in the sheet substrate 11 are in the above-described range, and the thickness of the light reflecting layer 12 provided on the sheet substrate 11 is 0.5 μm or more. By setting it within the range of 4 μm or less, it has high reflectivity, has excellent water barrier properties, moisture permeability and air permeability, and can maintain water resistance. The reason for this is not clear, but can be considered as follows. That is, in the case where the light reflecting layer 12 is provided on the surface of the sheet base material 11 in which the size (average diameter) and the number (void ratio) of the voids 13 are in a predetermined range, if the thickness of the light transmitting layer 12 is increased, Wetness and breathability are reduced. If the thickness of the light reflecting layer 12 is in the range of 0.5 μm or more and 4 μm or less, the light reflectance is maintained while maintaining moisture permeability and air permeability even if the gap 13 existing on the surface of the sheet substrate 11 is closed. It is thought that it can be improved. This is only an assumption, and the present invention is not limited thereto. In the present invention, the water vapor and carbon dioxide gas 15 that have passed through the sheet base material 11 are released into the atmosphere through the light reflecting layer 12. Moreover, the preferable thickness of the light reflection layer 12 is 1 micrometer or more and 2.5 micrometers or less.

The light reflecting layer 12 may be any layer that can reflect light in the visible region, and preferably has a color such as white or silver. Since these colors reflect light in the visible region, the light in the visible region is reflected on the surface of the sheet base material 11, thereby increasing the amount of light irradiated to the trees planted on the ground. . In this embodiment, the case where the light reflection layer 12 is a white ink layer formed including a white ink component will be described. The light reflecting layer 12 is not limited to the white ink layer, and may be a layer formed by containing ink components of other colors that can reflect light in the visible region such as silver.

(White ink component)
The white ink component contains a white powder and a resin component.

As the above white powder, a known white pigment can be used. Examples of white pigments include anatase type or rutile type titanium oxide, titanium oxides whose surfaces are treated with metal oxides such as Al and Si, and extender pigments such as calcium carbonate and barium sulfate, and other white pigments. And the like which can be used within a range not impeding the object of the present invention. The titanium oxide having an average particle size of 0.1 μm or more and 0.5 μm or less is preferably used. The white powder is preferably contained in the light reflecting layer 12 in the range of 10% by mass to 50% by mass.

The resin component is not particularly limited as long as it is a resin having the light scattering function, such as a polyurethane resin and a polyester resin, and a polyurethane resin is preferable. Polyurethane resins are preferred because they have little adverse effect on moisture permeability when used as a resin component (binder) in moisture permeable waterproof sheets. Examples of the polyurethane resin include resins such as polyester polyurethane, polyether polyurethane, polyether polyester polyurethane, polycarbonate polyurethane, and polycaprolactam polyurethane, and mixtures thereof.

The resin component has at least one selected from polyurethane resins having a glass transition temperature Tg (° C.) of −60 ° C. ≦ Tg ≦ 0 ° C. and a weight average molecular weight Mw of 10,000 ≦ Mw ≦ 80,000. Those that are seeds are preferably used. When the glass transition temperature Tg exceeds 0 ° C., the breaking strength and the Young's modulus of the sheet base material 11 increase, and accordingly, the brittleness becomes poor and the tearability decreases. On the other hand, when the glass transition temperature Tg is lower than −60 ° C., the toughness of the light reflecting layer 12 is lowered. On the other hand, when the mass average molecular weight of the polyurethane-based resin exceeds 80,000, the strength of the obtained light reflecting layer 12 increases, and accordingly, the brittleness becomes poor, and the tearability decreases. On the other hand, when the mass average molecular weight is less than 10,000, blocking occurs in the obtained light reflecting layer 12.

The above polyurethane-based resin can be obtained by reacting a polyisocyanate compound and a polymer polyol by a known method such as solution polymerization and using a chain extender and a reaction terminator in the urethane prepolymer as necessary. The polyurethane resin is not particularly limited as long as it satisfies the characteristic values of the resin component, and any polyurethane resin can be used. The above characteristic value is determined by various factors, and can be obtained, for example, by setting the amount of urethane groups constituting the polyurethane-based resin, the type and amount of polar groups, and the like.

The polyisocyanate compound is not particularly limited as long as it is used in the production of conventional polyurethane resins. For example, 1,6-hexamethylene diisocyanate, methylene diisocyanate, trimethylene diisocyanate, 2,2,4- or 2 , 4,4-trimethylhexamethylene diisocyanate, tetramethylene diisocyanate, 1,2-propylene diisocyanate, isopropylene diisocyanate, 1,3-butylene diisocyanate, etc .; 1,3- or 1,4-cyclohexane diisocyanate, isophorone Alicyclic isocyanates such as diisocyanate, 1,3-bis (isocyanatomethyl) cyclohexane, methyl-2,6-cyclohexane diisocyanate; m- or p-pheny Down diisocyanate, 4,4-diphenylmethane diisocyanate, 2,4- or 2,6-tolylene diisocyanate, and aromatic isocyanates such as naphthylene diisocyanate and the like.

In addition, examples of the polymer polyol include polyester polyols such as saturated hydrocarbon polyester polyols, polyether polyols, and polyether ester polyols.

Examples of the polyester polyol include a polyester polyol composed of a polyvalent carboxylic acid and a polyhydric alcohol, and a polyester polyol obtained by ring-opening polymerization of a lactone ring. Examples of the polyvalent carboxylic acid include aliphatic polyvalent carboxylic acids such as linear saturated hydrocarbons such as adipic acid, azelaic acid, succinic acid, and sebacic acid; unsaturated fatty acids such as fumaric acid and maleic acid. Aliphatic polycarboxylic acids; alicyclic polycarboxylic acids such as 1,4-cyclohexanedicarboxylic acid having a cyclohexyl group; aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, and terephthalic acid.

Examples of the polyhydric alcohol include ethylene glycol, diethylene glycol, 1,3-propylene glycol, dipropylene glycol, neopentyl glycol, triethylene glycol, xylylene glycol, polyethylene glycol, 1,2- or 1,3-propanediol. 1, 2-, 1,3- and 1,4-butanediol, 1,5-pentanediol and other aliphatic and alicyclic polyhydric alcohols and aromatic polyhydric alcohols.

Further, as the above polyether polyols, polyether polyols obtained by polymerizing oxirane compounds such as ethylene oxide and propylene oxide using a polyhydric alcohol such as ethylene glycol, 1,2-propanediol and glycerin as a polymerization initiator are used. Can be mentioned.

Further, examples of the polyether ester polyol include polyether ester polyols obtained by reacting the above polyether polyol with the above polyvalent carboxylic acid.

In addition to the above polyisocyanate compound and the above polymer polyol, the above polyurethane-based resin may contain ethylene glycol or diethylene glycol as necessary for adjustment of molecular weight, glass transition temperature, characteristic values of the above resin components, and the like. Resins of white ink components using chain extenders such as alcohols such as 1,2-propanediol, amines such as ethylenediamine and propylenediamine, and chain length terminators such as known lower alcohols and amines It is preferable to adjust the chain length in the components.

The above resin components can be used alone or in combination of a plurality of types, but are further cured to the above resin components in order to improve the tearability of the substrate on which the light reflecting layer 12 is applied. An agent can be added. Examples of the curing agent include the above aliphatic, alicyclic or aromatic polyisocyanate compounds, and other polyisocyanate compounds such as tolylene diisocyanate, hexamethylene diisocyanate, triphenyl methane triisocyanate, diphenylmethane diisocyanate, o- Toluidine diisocyanate, isophorone diisocyanate, 1,3,5-triisocyanate methylbenzene, lysine ester triisocyanate, etc., and multimers such as dimers and trimers derived from these isocyanate compounds, the above isocyanate compounds and 3 And polyisocyanates obtained by reaction with polyol compounds such as 3,3-trimethylolpropane. As the curing agent, specifically, Takenate D-110N (trade name) manufactured by Mitsui Takeda Chemical Co., Ltd. can be used.

The above resin component can be used alone, but is preferably contained in a proportion of 90% by mass or more and 100% by mass or less in the total amount of the binder. When the blending ratio of the resin component is less than 90% by mass, the tearability of the sheet substrate 11 is deteriorated, which is not preferable.

When using the above curing agent, the amount used is preferably in the range of 0.8% by mass or more and 10% by mass or less with respect to the resin component. When the blending ratio of the curing agent exceeds 10% by mass, the obtained light reflection layer 12 becomes brittle.

The white ink component is obtained by combining the white powder and the resin component with an organic solvent, for example, alcohols such as isopropyl alcohol and normal propyl alcohol, methyl acetate, ethyl acetate, butyl acetate, propyl acetate, ethyl lactate, and ethylene. Esters such as glycol acetate, ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone, ethers such as diethylene glycol methyl ether, tetrahydrofuran and dioxane, aromatics such as toluene and xylene, solvents such as halogenated hydrocarbons, and It is obtained by uniformly dispersing and kneading these mixed solvents by a known method.

(Additive)
In addition to the above white powder and resin component, the white ink component may contain various additives such as a resin component other than the above resin component, a plasticizer, and a dispersant, as long as it does not interfere with the purpose of the present invention. Can be added.

Examples of resin components other than the above resin components include cellulose derivatives such as nitrocellulose, cellulose propionate, cellulose acetate butyrate, cellulose diacetate, and cellulose triacetate, alkyd resins, acrylonitrile-butadiene copolymers, polyvinyl butyral, and styrene. Resin components that are compatible with the above resin components such as butadiene copolymers, polyester resins, and epoxy resins can be used in combination.

The light reflecting layer 12 is formed by coating on the surface of the sheet base material 11 by a coating method such as a known printing method. Examples of the coating method include a gravure coater, a reverse roll coater, a spray coater, a knife coater, a wire bar coater, an air knife coater, a doctor blade coater, a dipping coater, and a die coater, preferably a printing method using a gravure printing machine. Then, the light reflection layer 12 is formed by solid printing to a thickness (dry thickness) of 0.2 g / m ² or more and 0.7 g / m ² or less and drying. The drying conditions for the white ink component are not particularly limited as long as the above-described sheet base material 11 and the binder such as the resin component are not deteriorated, but are preferably dried at 70 ° C. or higher and 80 ° C. or lower.

<Agricultural sheet usage and crop cultivation method>
A method for cultivating crops using the above-described agricultural sheet will be described. As described above, the agricultural sheet 10 is a sheet formed by laminating the light reflecting layer 12 on the sheet base material 11 formed of plastic, and improves the reflectance of light incident on the agricultural sheet 10. Can be made. Therefore, it is possible to cultivate the agricultural product by laying the agricultural sheet 10 on the soil surface where the agricultural product is planted so that the surface on the sheet base material 11 side faces the soil side. The agricultural sheet 10 of the present invention can have high light reflectivity, has a long service life, has excellent moisture permeability and air permeability, and maintains high water resistance to prevent rainwater penetration. Can do.

The state of movement of moisture and carbon dioxide gas is shown in FIG. 5, the state of reflection of rain on the agricultural sheet 10 is shown in FIG. 6, and the state of reflection of sunlight on the agricultural sheet 10 is shown in FIG. For example, as shown in FIG. 5, the agricultural sheet 10 is laid on the surfaces of a base 31 a on which trees 32 such as citrus fruits and peaches on the soil (ground) 31 are installed, and a drain groove 31 b for agricultural water. Thus, the water and carbon dioxide evaporated from the ground 31 pass through the light reflecting layer 12 through the gaps in the sheet base material 11. For this reason, since the said water | moisture content and carbon dioxide gas are trapped by the ground 31 under the agricultural sheet | seat 10, and the moisture content in soil can be kept high, drying of the ground can be suppressed. Moreover, as shown in FIG. 6, since the sheet | seat base material 11 can suppress the penetration | invasion of the rain etc. from the outside, even when it rains, rainwater is applied to the ground 31 covered with the agricultural sheet 10. Reaching can be suppressed. In general, in the cultivation of fruit trees and the like, in order to improve the sugar content of fruits, it is important to evaporate moisture in the soil to keep the soil in an appropriate dry state and to prevent rainwater from penetrating into the soil. It is also important to release carbon dioxide in the soil to the outside air in order to prevent a decline in tree vigor. Therefore, if the agricultural sheet 10 is used, the moisture content in the soil can be kept high and the ground can be kept in an appropriate dry state, so that the growth and fruiting of the trees 32 and the adverse effects on the fruits can be suppressed. it can. Thereby, since the sugar content of a fruit can be improved and the fall of tree vigor can be suppressed, the fall of the quality of fruit trees can be suppressed.

Further, as shown in FIG. 7, the agricultural sheet 10 is provided with a light reflecting layer 12 on the surface of the sheet base material 11, and the light reflecting layer 12 is a layer formed using a resin component containing a white ink component. The layer has high opacity and whiteness. Generally, in the cultivation of fruit trees and the like, it is important to irradiate fruit trees with light scattered by reflecting sunlight on the ground in order to promote the coloring of fruits. The agricultural sheet 10 has a high reflectance of sunlight because the whiteness of the light reflection layer 12 is high. Since the reflectance of sunlight is improved in the light reflecting layer 12, sunlight is reflected on the sheet surface of the agricultural sheet 10, and is applied to crops such as citrus fruits and deciduous fruit trees that grow on trees planted on the ground. The irradiation ratio of the light reflected by the sheet base material 11 can be improved. Moreover, since the light quantity which sunlight reaches | attains the ground side of the agricultural sheet | seat 10 can be reduced, it can suppress that weed grows on the ground 31. FIG.

Therefore, by using the agricultural sheet 10, it is possible to improve the production efficiency of agricultural products such as citrus fruits and deciduous fruit trees that grow on the trees 32 planted on the ground 31. In addition, since the agricultural sheet 10 has excellent water shielding, moisture permeability, air permeability, and high water resistance, it is only necessary to lay the agricultural sheet once on the ground. Since it is no longer necessary to perform operations such as laying on the ground and removing the agricultural sheet 10 from the ground 31, it is possible to perform agricultural work without being affected by the weather, and greatly improve the workability of agricultural work Can do.

When the agricultural sheet 10 is used on the ground such as cultivated soil, the agricultural sheet 10 can be easily applied according to the shape of the ground. An example of the cultivated soil when the agricultural sheet 10 is applied to the cultivated soil is shown in FIG. As shown in FIG. 8, when a plurality of drainage grooves 31b for agricultural water are provided in parallel at a predetermined interval and a plurality of trees 32 are provided at a predetermined interval on the base 31a, the agricultural sheet 10 includes the base 31a and the agriculture. It is laid so as to cover the entire surface of the drainage groove 31 for water. A cut is made in the agricultural sheet 10 so as to correspond to the trunk portion of the tree 32 installed on the base 31a corresponding to each section, and the agricultural sheet 10 is attached to the trunk of the tree 32 with a plastic tape, etc. Thus, rainwater may not reach the root. In addition, it is desirable that there is no gap as much as possible between the outer periphery of the trunk of the tree 32 and the cut line of the agricultural sheet 10, but even if there is a gap, rain intrudes into the ground 31 due to branches and leaves. Therefore, the moisture permeability, breathability, water resistance and durability of the agricultural sheet 10 are not affected.

Further, when a plurality of drainage grooves 31b for agricultural water are provided in parallel at a predetermined interval in one direction, the operation of providing the drainage grooves 31b for agricultural water can be easily performed. Therefore, for example, when multi-cultivation is introduced into an orchard that has already been produced, it is preferable to provide a plurality of drain grooves 31b for agricultural water in parallel at predetermined intervals in one direction. In addition, since the agricultural water discharge groove 31b is provided for collecting and draining water, the agricultural sheet 10 located on the agricultural water discharge groove 31b from the viewpoint of reducing the cultivation cost. The conventional vinyl sheet such as vinyl chloride resin or polyethylene resin may be used.

In addition, although FIG. 8 demonstrated the case where the discharge groove | channel 31b for agricultural water was provided with two or more parallelly with the predetermined space | interval, this invention is not limited to this. FIG. 9 shows another example of the cultivated soil when the agricultural sheet 10 is applied to the cultivated soil. As illustrated in FIG. 9, the agricultural water discharge grooves 31 b may be provided in a lattice shape, and the agricultural water discharge grooves 31 b may be provided in a lattice shape so as to surround the trees 32 one by one. As shown in FIG. 9, when the drainage grooves 31b for agricultural water are provided in a lattice shape, drainage efficiency is high and moisture control of the soil can be easily performed. Further, compared to the case where a plurality of agricultural water drain grooves 31b are provided in parallel at a predetermined interval as shown in FIG. 8, it is easier to control soil moisture when the agricultural water drain grooves 31b are provided in a grid pattern. However, it takes time to provide the discharge groove 31b for agricultural water. Therefore, when making the cultivation place for multicultural planning from the beginning, or when multiculturing is planned at the time of rooting, it is preferable to provide the grid-like drainage grooves 31b for agricultural water.

Next, the present invention will be specifically described with reference to examples. However, the present invention is not limited at all by these examples.

<Example 1>
(Manufacture of sheet substrate 1)
As a resin composition for the base material layer constituting the sheet base material 1, 65.5% by mass of a propylene homopolymer (manufactured by Nippon Polychem Co., Ltd., trade name “NOVATEC PP: MA-8”, melting point 164 ° C.) Carbonate having 6.5% by mass of high-density polyethylene (manufactured by Nippon Polychem Co., Ltd., trade name “Novatech HD: HJ580”, melting point 134 ° C., density 0.960 g / cm ³ ), and an average particle size of 1.5 μm An unstretched sheet (thermoplastic resin sheet) was obtained from the resin composition containing 28% by mass of calcium powder using an extruder. Next, this unstretched sheet was stretched 4 times in the longitudinal direction to obtain a uniaxially stretched sheet. In addition, a vertical direction is an extrusion direction when a resin composition is extruded using an extruder.

On the other hand, as the resin composition for the surface layer constituting the sheet substrate 1, the same material as described above was used, 51.5% by mass of propylene homopolymer, 3.5% by mass of high-density polyethylene, and average particles A resin composition containing 42% by mass of calcium carbonate powder having a diameter of 1.5 μm and 3% by mass of titanium oxide powder having an average particle diameter of 0.8 μm is melt-kneaded using another extruder, Extruded from the die on both sides of the surface of the uniaxially stretched sheet base material and laminated on both surfaces of the above uniaxially stretched sheet base material to obtain a laminated sheet (laminate) having a layer structure of surface layer / base material layer / surface layer .

Next, this laminated sheet was stretched 7 times in the transverse direction and the ears were slit to form a fine void having a layer structure of surface layer (15 μm) / base material layer (40 μm) / surface layer (15 μm) and a thickness of 70 μm. The sheet | seat base material 1 containing this was obtained. At this time, the average diameter of the entire voids of the sheet substrate 1 was 20 μm, the void ratio was 55%, and the opacity was 93%. In addition, the average diameter of the space | gap of the sheet | seat base material 1, the porosity, and the opacity were performed using the method as described in the said embodiment.

(Formation of white ink layer)
The following components were uniformly kneaded and dispersed to prepare a white ink. This white ink was solid-printed to 2 μm (dry thickness) at a drying temperature of 80 ° C. using a gravure printing machine and dried to form a white ink layer as a light reflecting layer.
・ Polyurethane resin (made by Arakawa Chemical Industry Co., Ltd., trade name “Yuriano 2466”): 40.0 parts ・ Nitrified cotton (made by Inabata Sangyo Co., Ltd., trade name “DLX5-8”): 2.0 parts Titanium oxide (trade name “JR-800” manufactured by Teika Co., Ltd.): 39.0 parts, curing agent (trade name “Takenate D-110N” manufactured by Mitsui Takeda Chemical Co., Ltd.): 4.0 parts, solvent (Isopropyl alcohol: 5.0 parts, methyl ethyl ketone: 6.0 parts, ethyl acetate: 4.0 parts)

<Example 2>
(Manufacture of sheet base material 2, formation of white ink layer)
Instead of the sheet substrate 1 of Example 1, the surface layer (5 μm) / the substrate layer (20 μm) / the surface layer (5 μm) having the same layer structure as the sheet substrate 1 of Example 1 and having a thickness Was performed in the same manner as in Example 1 except that the sheet base material 2 containing fine pores of 30 μm was used.

<Example 3>
(Manufacture of sheet base material 3, formation of white ink layer)
Instead of the sheet substrate 1 of Example 1, the surface layer (20 μm) / the substrate layer (50 μm) / the surface layer (20 μm) has the same layer structure as the sheet substrate 1 of Example 1, and has a thickness. Was carried out in the same manner as in Example 1 except that the sheet substrate 3 containing fine voids of 90 μm was used.

<Example 4>
(Manufacture of sheet base material 4, formation of white ink layer)
The average diameter of the entire voids of the sheet substrate 1 of Example 1 was adjusted to 3 μm, and the laminated sheet was stretched 7 times in the lateral direction to obtain a surface layer (15 μm) / base material layer (40 μm) / surface layer. This was carried out in the same manner as in Example 1 except that the sheet base material 4 was changed to a sheet substrate 4 containing a fine gap having a thickness of 70 μm with a layer structure of (15 μm).

<Example 5>
(Manufacture of sheet base material 5, formation of white ink layer)
The overall porosity of the sheet substrate 1 of Example 1 was adjusted to 35%, and the laminated sheet was stretched 7 times in the lateral direction to obtain a surface layer (15 μm) / base material layer (40 μm) / surface layer ( 15 μm), and the same procedure as in Example 1 was performed except that the sheet base material 5 was changed to a sheet substrate 5 containing fine voids having a thickness of 70 μm.

<Example 6>
(Manufacture of sheet substrate 1, formation of white ink layer)
This was carried out in the same manner as in Example 1 except that the thickness of the white ink layer was changed so that the thickness of the white ink layer in Example 1 was 4 μm.

<Comparative Example 1>
(Manufacture of sheet substrate 1, formation of white ink layer)
This was carried out in the same manner as in Example 1 except that no white ink layer was formed on the surface of the sheet substrate 1 of Example 1.

<Comparative example 2>
(Manufacture of sheet substrate 1, formation of white ink layer)
This was performed in the same manner as in Example 1 except that the thickness (dry thickness) of the white ink layer formed on the sheet substrate 1 of Example 1 was changed to 5 μm.

<Comparative Example 3>
(Manufacture of sheet substrate 1, formation of white ink layer)
This was performed in the same manner as in Example 1 except that the thickness (dry thickness) of the white ink layer formed on the sheet substrate 1 of Example 1 was changed to 0.4 μm.

<Comparative example 4>
(Manufacture of sheet base material 6, formation of white ink layer)
The average diameter of the entire voids of the sheet substrate 1 of Example 1 was adjusted to 0.8 μm, and the laminated sheet was stretched 7 times in the lateral direction to obtain a surface layer (15 μm) / substrate layer (40 μm) / This was carried out in the same manner as in Example 1 except that the surface base layer (15 μm) was changed to the sheet base material 6 containing a fine void having a thickness of 70 μm.

<Comparative Example 5>
(Manufacture of sheet base material 7, formation of white ink layer)
The overall porosity of the sheet substrate 1 of Example 1 was adjusted to be 30%, the laminated sheet was stretched 7 times in the lateral direction, and the surface layer (15 μm) / substrate layer (40 μm) / surface layer ( The same procedure as in Example 1 was performed except that the sheet base material 7 was changed to a sheet base material 7 having a thickness of 70 μm and a thickness of 15 μm.

Table 1 below shows the thickness of each sheet base material, the average diameter of the voids, the void ratio, the opacity, and the thickness of the white ink layer in each of Examples 1 to 6 and Comparative Examples 1 to 5. Show.

<Evaluation of visible light reflectance>
An ultraviolet / visible / near-infrared spectrophotometer (trade name “UV-3600”, manufactured by Shimadzu Corporation) using an integrating sphere attachment device (ISR-3100) with an incident angle of 8 ° and a visible region of 500 nm, The reflectance (total reflectance) at 600 nm and 700 nm was measured. The measured reflectance was evaluated according to the following criteria.
A: The reflectance was 100% over the entire visible region.
○: The minimum reflectance was 90% or more and less than 100% in the visible region.
(Triangle | delta): Some had the minimum reflectance less than 90% in a visible region.
The evaluation results were as shown in Table 2 below. In addition, the unit of the numerical value in Table 1 is%.

<Evaluation of moisture permeability>
Two 200 ml transparent cups (clear cup hard) were prepared for each specimen. Add 60 ml of 60 ° C. warm water to one side. Immediately place a 10cm square sheet sample on top of the cup and place the rest of the cup on top of it (press a 50g weight on top of the cup so that the cup flange and flange are tight. After 20 minutes, it was visually confirmed whether the cup was clouded with water vapor that had passed through the sheet in the upper cup. The moisture permeability was evaluated according to the following criteria.
A: Cloudy water droplets were observed on the entire surface of the upper cup, and moisture permeability was observed.
○: More than half of the side surface of the upper cup was cloudy and moisture permeability was observed.
Δ: The side surface of the upper cup was clouded by 1/3 or more, but moisture permeability was observed (however, the moisture permeability is the lowest level as a product).
X: The upper cup was not cloudy and moisture permeability was not observed.
The evaluation results were as shown in Table 2 below.

As is clear from the evaluation results in Table 2, it was confirmed that the reflectance of visible light could be improved by providing a white ink layer on the sheet substrate 1. Moreover, when providing a white ink layer in the sheet | seat base material 1, it confirmed that the reflectance of visible light was improved and moisture permeability was expressed by making the film thickness of the white ink layer into the predetermined range. It was done.

DESCRIPTION OF SYMBOLS 10 Agricultural sheet 11 Sheet base material 11a Base material sheet base material 11b Surface layer sheet base material 12 Light reflecting layer 13 Void 15 Water vapor and carbon dioxide 21, 21a, 21b Thermoplastic resin sheet 22 Laminate 31 Soil (ground )
31a Foundation 31b Drainage for agricultural water 32 Trees

Claims (8)

1. An agricultural sheet comprising a sheet substrate and a light reflecting layer provided on at least one surface side of the sheet substrate,
   The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
   An agricultural sheet, wherein the light reflecting layer has a thickness in a range of 0.5 μm or more and 4 μm or less.
2. The agricultural sheet according to claim 1, wherein the porous thermoplastic resin sheet comprises a polypropylene resin.
3. The agricultural sheet according to claim 1 or 2, wherein the porous thermoplastic resin sheet is stretched in at least a uniaxial direction.
4. The agricultural sheet according to claim 3, wherein the sheet base material is obtained by laminating two or more layers of the stretched porous thermoplastic resin sheet.
5. The agricultural sheet according to claim 4, wherein the sheet base material is formed by laminating two or more layers so that the stretching axis directions of the respective porous thermoplastic resin sheets are orthogonal to each other.
6. The agricultural sheet according to any one of claims 1 to 5, wherein the light reflecting layer comprises a white pigment and a polyurethane resin.
7. A method for cultivating crops using an agricultural sheet,
   The agricultural sheet includes a sheet base material, and a light reflection layer provided on at least one surface side of the sheet base material,
   The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
   The thickness of the light reflecting layer is in the range of 0.5 μm or more and 4 μm or less,
   A method for cultivating a crop, characterized in that the agricultural sheet is laid on the surface of the soil on which the crop is planted so that the surface on the sheet substrate side faces the soil.
8. A method of using an agricultural sheet,
   The agricultural sheet includes a sheet base material, and a light reflection layer provided on at least one surface side of the sheet base material,
   The sheet base material has voids having an average diameter in the range of 1 μm or more and 50 μm or less, the porosity is in the range of 35% or more and 60% or less, and the thickness is 30 μm or more and 90 μm or less. Is a porous thermoplastic resin sheet in the range of
   The thickness of the light reflecting layer is in the range of 0.5 μm or more and 4 μm or less,
   A method for using an agricultural sheet, characterized in that the agricultural sheet is laid on the soil surface so that the surface on the sheet base material side faces the soil.

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